Retinal prosthesis techniques

ABSTRACT

Apparatus for use with an external non-visible light source is provided. The apparatus comprises an intraocular device configured for implantation in a human eye, and comprising an energy receiver. The energy receiver is configured to receive light emitted from the external non-visible light source, and extract energy from the emitted light for powering the intraocular device. The intraocular device is configured to regulate a parameter of operation of the intraocular device based on a modulation of the light emitted by the external non-visible light source and received by the energy receiver. Other embodiments are also described.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application is a continuation-in-part of U.S. patentapplication Ser. No. 12/852,218 to Gefen et al., entitled, “Retinalprosthesis techniques”, filed Aug. 6, 2010, now published as U.S. PatentPub. No. 2012/0035725, which is incorporated herein by reference.

FIELD OF EMBODIMENTS OF THE INVENTION

Some applications of the invention relate generally to implantablemedical devices and more specifically to a retinal prosthesis.

BACKGROUND

Retinal malfunction, due to degenerative retinal diseases, is a leadingcause of blindness and visual impairment. Implantation of a retinalprosthesis is a technology for restoring some useful vision inindividuals suffering from retinal-related blindness.

The retina is a multi-layered light-sensitive structure that lines theposterior, inner part of the eye. The retina contains photoreceptorcells, for example rods and cones, which capture light and convert lightsignals into neural signals transmitted through the optic nerve to thebrain. Rods are responsible for light sensitive, low resolution blackand white vision, whereas cones are responsible for high resolutioncolor vision. Most cones lie in the fovea, which defines the center ofthe retina. A bipolar cell layer exists between the photoreceptors andganglion cells of the retina. The bipolar cell layer transmits signalsfrom the photoreceptors to the ganglion cells whose axons form the opticnerve and transmit visual information to the brain.

SUMMARY OF APPLICATIONS OF THE INVENTION

In some applications of the present invention, a system is provided forrestoring at least partial vision in a subject suffering from a retinaldisease. The system comprises an apparatus comprising an externaldevice, comprising a mount that is placed in front of the subject's eye.The mount may be, for example, a pair of eyeglasses. The external devicefurther comprises a power source, for example a laser that is coupled tothe mount and is configured to emit radiated energy that is outside thevisible range directed toward the subject's eye.

The apparatus additionally comprises an intraocular device, which isimplanted entirely in the subject's eye. The intraocular devicecomprises an intraocular retinal prosthesis, configured to be implantedin the subject's eye in either an epi-retinal or a sub-retinal position.

The intraocular device typically comprises a support substrate and anarray of electrodes protruding from the support substrate. (In thiscontext, in the specification and in the claims, “array” is meant toinclude rectangular as well as non-rectangular arrays (such as circulararrays). The protruding electrodes are shaped to defineelectrically-exposed tips which penetrate retinal tissue of the subject,bringing the electrodes in contact with the tissue. For someapplications, a surface of the electrodes is treated to increaseroughness and surface area of the electrodes, thus reducing electrodeimpendence and facilitating retinal stimulation and/or axonregeneration. Additionally or alternatively, the exposed tips of theelectrodes have perforations passing therethrough, further increasingthe surface area of the electrodes and allowing neuronal processes, topass through and intertwine with the electrodes.

For some applications, the support substrate from which the electrodesprotrude comprises additional elements of a retinal prosthesis, e.g., anenergy receiving layer, a photosensor layer and driving circuitry thatis powered by the energy receiving layer. The driving circuitrytypically drives electrical charge into the retinal tissue from the tipsof the electrodes, in response to sensing by the photosensor layer, inorder to stimulate the retinal tissue.

For some applications, the photosensor layer is divided into units, eachunit corresponding to a stimulating electrode in the array ofelectrodes.

The inventors have identified that, for some applications, sufficientstimulation of retinal tissue is a characteristic for consideration inenabling proper function of a retinal prosthesis. In particular,facilitating stimulation of the bipolar cell layer of the retina, whichin turn stimulates ganglion cells, is a characteristic for considerationin retinal prosthesis provided by some applications of the presentinvention. The ganglion cells, whose axons form the optic nerve, furthertransmit the visual information to the brain resulting in the formationof an image. Penetrating perforated electrodes, in contrast to surfaceelectrodes known in the art which sit on the surface of tissue, areconfigured to extend from either an epi-retinal or a sub-retinalimplantation site and penetrate retinal tissue to directly contact anddrive electrical charge into the bipolar cell layer from typically lessthan 10 um from the nearest bipolar cell. Rough electrode surfaces andperforations passing through the electrodes allow neuronal processes togrow therethrough, further improving cell-electrode coupling andincreasing stimulation. Increased and direct contact of the retinaltissue by penetrating perforated electrodes enhances stimulation of theretina resulting in enhanced image resolution.

There is therefore provided in accordance with some applications of thepresent invention, apparatus for use with an external non-visible lightsource, the apparatus including:

an intraocular device configured for implantation in a human eye, andincluding an energy receiver configured to:

-   -   receive light emitted from the external non-visible light        source, and    -   extract energy from the emitted light for powering the        intraocular device,

the intraocular device is configured to regulate a parameter ofoperation of the intraocular device based on a modulation of the lightemitted by the external non-visible light source and received by theenergy receiver.

For some applications, the intraocular device is configured to regulatethe parameter of operation of the intraocular device based on amplitudemodulation of the light emitted by the external non-visible light sourceand received by the energy receiver.

For some applications, the intraocular device is configured to regulatethe parameter of operation of the intraocular device based on theamplitude modulation of the light, the modulation of the light varyingbetween a minimum signal level and a maximum signal level, the minimumsignal level being at least 20% of the maximum signal level.

For some applications, the intraocular device is configured to regulatethe parameter of operation of the intraocular device based on theamplitude modulation of the light, the minimum signal level being atleast 50% of the maximum signal level.

For some applications, the intraocular device is configured to regulatethe parameter of operation of the intraocular device based on theamplitude modulation of the light, the modulation of the light beingbased on a carrier frequency of the modulated light being between 10 kHzand 100 kHz.

For some applications, the intraocular device is configured to regulatethe parameter of operation of the intraocular device based on theamplitude modulation of the light, the light being received by theintraocular device in pulses having a pulse width of 1-10 usec.

For some applications, the external non-visible light source includes asensor configured to sense a level of ambient light, the externalnon-visible light source modulating the light emitted by the externalnon-visible light source based on the level of ambient light, and theenergy receiver is configured to receive ambient light and the lightemitted from the external non-visible light source and to regulate theparameter of operation of the intraocular device based on amplitudemodulation of the light.

For some applications, the energy receiver is configured to receiveambient light and the light emitted from the external non-visible lightsource, and the apparatus further includes a filter associated with theenergy receiver, and configured to reduce a level of the ambient lightfrom reaching the energy receiver.

For some applications, the energy receiver is configured to receiveambient light and the light emitted from the external non-visible lightsource, the modulation of the light varying between a minimum signallevel and a maximum signal level, the minimum signal level being atleast 20% of a summed strength of the received light emitted from theexternal non-visible light source and the received ambient light.

For some applications, the energy receiver is configured to receive thelight emitted from the external non-visible light source and the ambientlight, the minimum signal level being at least 50% of the summedstrength of the received light emitted from the external non-visiblelight source and the received ambient light.

For some applications, the intraocular device is configured to regulatethe parameter of operation of the intraocular device based on frequencymodulation of the light emitted by the external non-visible light sourceand received by the energy receiver.

For some applications, the intraocular device is configured to regulatethe parameter of operation of the intraocular device based on thefrequency modulation of the light, the modulation of the light beingbased on a carrier wave having a frequency between 10 kHz and 100 kHz.

For some applications, the intraocular device is configured to regulatethe parameter of operation of the intraocular device based on thefrequency modulation of the light, the light being received by theintraocular device in pulses having a pulse width of 1-10 usec.

For some applications, the non-visible light source is configured toemit light that is outside of 380-750 nm and the intraocular device isconfigured to receive the light that is outside of 380-750 nm.

For some applications, the parameter of operation includes an intensityof the electrical current applied to the retina, and the apparatus isconfigured to regulate the intensity of the electrical current appliedto the retina, based on the modulated light.

For some applications, the apparatus includes driving circuitry, and theenergy receiver is configured to extract energy from the emitted light,for powering the intraocular device, and, the apparatus is configured,while extracting the energy, to receive ambient light and, responsively,transmit a signal to the driving circuitry.

For some applications, the energy receiver is configured to receive theambient light and to transmit the signal to the driving circuitry.

For some applications, the apparatus includes driving circuitry, and theenergy receiver is configured to extract energy from the emitted light,for powering the intraocular device, and, the apparatus is configured,during periods which alternate with the extracting of the energy, toreceive ambient light and, responsively, transmit a signal to thedriving circuitry.

For some applications, the energy receiver is configured to receive theambient light and to transmit the signal to the driving circuitry.

For some applications, the intraocular device is configured todemodulate the modulated energy and, in response, regulate the operationparameter of the intraocular device.

There is further provided, in accordance with some applications of thepresent invention, an external device for association with anintraocular implant, the device including:

a power source including a modulator, the power source configured toemit non-visible light to the implant for transmitting power to theimplant when the implant is located in the eye, the emitted light beingmodulated with a coded signal, such that, when the light is transmittedto the implant, the implant receives power and is controlled by thecoded signal.

For some applications, the power source is configured to modulate thelight with the coded signal using amplitude modulation of the lightemitted by the power source.

For some applications, the power source is configured to modulate thelight to vary between a minimum signal level and a maximum signal level,and the minimum signal level is at least 20% of the maximum signallevel.

For some applications, power source is configured to set the minimumsignal level to be at least 50% of the maximum signal level.

For some applications, the power source is configured to set a carrierfrequency of the modulated light to be between 10 kHz and 100 kHz.

For some applications, the power source is configured to set a pulsewidth of pulses of the light to be 1-10 usec.

For some applications, the modulator is configured to modulate the lightemitted from the power source between a minimum signal level and amaximum signal level, the minimum signal level being at least 20% of asummed strength of the light emitted from the power source and ambientlight.

For some applications, the modulator is configured to modulate the lightemitted from the power source to be at least 50% of the summed strengthof the light emitted from power source and the ambient light.

For some applications the external device includes a sensor configuredto sense a level of the ambient light, the modulator is configured tomodulate the light emitted by the power source based on the level ofambient light.

For some applications, the power source is configured to set awavelength of the emitted light to be outside of 380-750 nm.

For some applications, the power source is configured to emit the lightand to not include image information in the emitted light.

For some applications, the modulator is configured to control a pulsefrequency of electrical current applied to the retina by the implant, bymodulating the emitted light with the coded signal.

For some applications the external device includes a mount that iscoupled to the power source and is configured to be placed in front ofan eye of a subject.

For some applications, the mount includes a pair of eyeglasses.

For some applications the external device includes apartially-transparent mirror coupled to the mount and configured todirect the non-visible light to the implant.

For some applications, the partially-transparent mirror is configured toallow ambient light to pass through to the implant.

There is still further provided, in accordance with some applications ofthe present invention, an intraocular device configured to be implantedentirely in a subject's eye, the intraocular device including:

a plurality of photosensors configured to receive an ambient imagethrough a lens of the eye; and

an energy receiver configured to receive non-visible light through thelens of the eye and to extract power from the light for powering thephotosensors,

the energy receiver is adapted to receive the light while the pluralityof photosensors receive the ambient image.

For some applications, the energy receiver is additionally configured toreceive visible light.

There is additionally provided, in accordance with some applications ofthe present invention, an intraocular implant, including:

a photosensor array adapted for implantation in a human eye;

an energy receiver adapted for implantation in the human eye and furtheradapted to receive a power signal in the form of a non-visible lightbeam; and

a filter associated with the photosensor array, configured tosubstantially prevent the power signal from reaching the photosensorarray.

For some applications, the energy receiver is additionally configured toreceive visible light.

For some applications, the photosensor array is configured to receivevisible light, and the intraocular device further includes a filterassociated with the energy receiver, configured to reduce a level ofambient light that reaches the energy receiver.

There is yet additionally provided, in accordance with some applicationsof the present invention, apparatus including:

an intraocular device, including at least one receiver configured forimplantation in a human eye, the at least one receiver having an imagereception portion and an energy reception portion configured to receivea power signal from a non-visible light beam; and

at least one control unit configured to prevent reception of at least aportion of the power signal by the image reception portion.

For some applications, the control unit is configured for implantationin the eye.

For some applications the apparatus includes a mount that is configuredto be placed in front of the eye of the subject, and the control unit iscoupled to the mount.

For some applications, the control unit is configured to prevent energyreception by the image reception portion, by sending a control signal toterminate the power signal.

For some applications the apparatus includes a filter, the control unitis configured to prevent energy reception by sending a control signal toactivate the filter.

For some applications, the control unit is configured to prevent energyreception, by sending a control signal to deactivate the image receptionportion.

For some applications, the energy reception portion is additionallyconfigured to receive visible light.

There is still additionally provided, in accordance with someapplications of the present invention, an intraocular device configuredfor epi-retinal implantation in a subject's eye, and configured for usewith a plurality of photosensors, each photosensor configured to detectambient photons and to generate a signal in response thereto, theintraocular device including:

a plurality of stimulating electrodes configured to penetrate a retinallayer of the subject's eye; and

driving circuitry, coupled to the photosensors, and configured to drivethe electrodes to apply electrical pulses to a retina of the eye inresponse to the signal from the photosensors,

the driving circuitry is configured to vary a frequency of the pulsesbased on intensity of the ambient photons received by the photosensors.

For some applications, the intraocular device includes the plurality ofphotosensors.

For some applications, the driving circuitry is further configured tovary a parameter of the electrical pulses selected from the groupconsisting of: a number of the pulses, duration of each pulse, and apulse repetition interval of the pulses.

For some applications, the driving circuitry is configured to reducesub-harmonics by jittering the pulse frequency.

The present invention will be more fully understood from the followingdetailed description of embodiments thereof, taken together with thedrawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a system for restoring at least partial vision in a subjectin accordance with some applications of the present invention;

FIGS. 2A-B are schematic illustrations of an array of penetratingelectrodes, in accordance with some applications of the presentinvention;

FIG. 3 is a schematic cross-sectional illustration of a pointed tip anof electrode, in accordance with some applications of the presentinvention;

FIGS. 4A-B are schematic illustrations of an intraocular device forretinal stimulation, in accordance with some applications of the presentinvention;

FIG. 5 is a schematic illustration of an intraocular device for retinalstimulation, in accordance with some applications of the presentinvention;

FIG. 6 is a schematic illustration of an array of penetratingelectrodes, in accordance with some applications of the presentinvention;

FIG. 7 is a schematic illustration of an intraocular device penetratingretinal tissue, in accordance with some applications of the presentinvention;

FIG. 8 is a block diagram of the transmission of energy, information,and instructions, in the system for restoring vision, in accordance withsome applications of the present invention;

FIGS. 9A-C are schematic illustrations of the system for restoringvision, in accordance with some applications of the present invention;

FIG. 10 is a block diagram of transmission of energy, information, andinstructions, in the system for restoring vision, in accordance withsome applications of the present invention; and

FIGS. 11A-B are block diagrams of transmission of energy, information,and instructions, in the system for restoring vision, in accordance withsome applications of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1 shows a system 20 for restoring at least partial vision in asubject, a portion of which is implanted in an eye of the subject, inaccordance with some applications of the present invention.

Vision is initiated when light reflecting from objects is focused bylens 2 of eye 4 onto the retina 6. FIG. 1 shows a cross section of aportion of a human retina. The retina is approximately 0.2-0.5 mm thickand lines the back of the eye. As shown, the retina consists of threelayers of neurons: photoreceptor cells 10, ganglion cells 12 and manyinterneurons 15 packed into the central part of the section of theretina intervening between the photoreceptors and the ganglion cells.The ganglion cells, which transmit visual information to the brain, lieinnermost (as used herein) in the retina, i.e., on the side of theretina closest to the lens and front of the eye. The photoreceptor cells(e.g., rods and cones), which capture light and convert light signalsinto neural signals, lie outermost in the retina. The central part ofthe section of retina located between the photoreceptors and theganglion cells includes the inner nuclear layer (INL), which is made upof bipolar cells 14 and other cells. Interneurons 15, e.g., horizontalcells and amacrine cells, facilitate regulation of the neural signalfrom the photoreceptors and the bipolar cells.

Bipolar cells 14 typically transmit signals from photoreceptors 10 toganglion cells 12. The rod and cone photoreceptors transfer a signal tothe bipolar cells that lay adjacent to the photoreceptor layer. Thebipolar cells then transmit the signal to the ganglion cells whose axonsform the optic nerve. The bipolar cell 14 are generally located in aregion of the retina that is approximately 130 um-200 um from the innerlimiting membrane (ILM), which is the boundary between the vitreoushumor in the posterior chamber and the retina itself.

As shown in FIG. 1, for some applications, an intraocular device 60 isimplanted in an epi-retinal position, typically coupled to the ILM. Asdescribed in Zrenner, 2002, which is incorporated herein by reference,epi-retinal arrays are typically implanted onto the retinal surface thatseparates the retinal neural layer from the vitreous body of the eye'sposterior chamber, such that the implant is typically located outside ofthe vitreous body, contacting the ILM. As appropriate, techniquesdescribed in one or more of these references may be adapted for use inimplanting device 60.

For some applications, device 60 is implanted in a sub-retinal position(not shown). As described in Zrenner, 2002, which is incorporated hereinby reference, sub-retinal arrays are typically implanted between thepigment epithelial layer 30 and the layer of the retina which containsphotoreceptor cells 10.

As provided by some applications of the present invention, device 60comprises a support substrate 62 and a plurality of electrodes 64protruding from the support substrate. Support substrate 62 comprisescomponents of an intraocular retinal prosthesis. For example, supportsubstrate 62 may comprise an energy receiving layer, a photosensor layerand driving circuitry. The driving circuitry is powered by the energyreceiving layer, which typically receives energy from an external device600 comprising an external power source 24 (e.g., a laser coupled to theframe of a pair of eyeglasses 25, and/or a radiofrequency (RF) powersource, and/or another electromagnetic power source). For someapplications a partially-transparent (e.g., half-silvered) mirror 23 iscoupled to eyeglasses 25, providing ophthalmoscope functionality to theexternal device.

It is to be noted that for some applications, techniques and apparatusdescribed herein with reference to the external and intraocular devicesmay be performed with techniques and apparatus described in U.S. patentapplication Ser. No. 12/368,150 to Gross et al., entitled, “RetinalProsthesis,” filed Feb. 9, 2009, now issued as U.S. Pat. No. 8,150,526;U.S. patent application Ser. No. 12/687,509 to Gefen et al., entitled“Penetrating electrodes for retinal stimulation, filed Jan. 14, 2010,now published as U.S. Patent Pub. No. 2011/0172736; and/orPCT/IL2010/000097 to Gross et al., entitled “Retinal Prosthesis,” filedFeb. 3, 2010, now published as WO/2010/089739, all of which are assignedto the assignee of the present patent application and are incorporatedherein by reference.

The driving circuitry drives electrodes 64 to apply electrical chargesto the retina, in response to sensing by the photosensor layer, in orderto stimulate the retina 6. Accordingly, system 20 for restoring visionin a subject does not comprise an extraocular camera, and intraoculardevice 60 does not receive image data from outside the eye, but ratherutilizes the intact optics and processing mechanisms of the eye 4.

Intraocular device 60 typically comprises approximately 500-6000, e.g.,1000-4000, typically 1600 electrodes 64. For some applications, theelectrodes protrude perpendicularly at least 50 um from the supportsubstrate.

Each electrode is typically 100-1000 um in length e.g., 300-600 um, forexample, 400 um, in order to reach the outer plexiform layer (OPL),where connections between the bipolar cells and the adjacentphotoreceptor cells occur. For some applications, each electrodecomprises an electrically-insulated body portion 68 coupled to anelectrically exposed tip portion 70. Insulated portion 68 of theelectrode has a length L1 of between 100 um and 650 um, e.g., 150 um.Exposed tip 70 of electrode 64 typically has a length L2 of between 25um and 100 um, e.g., 50 um. Typically, electrode 64 has an exposed areaof 750 um2. The electrodes 64 protrude from support substrate 62, suchthat when device 60 is implanted in an eye of a subject, electrodes 64penetrate tissue of retina 6 and exposed tip portions 70 are typicallydisposed in layer of bipolar cells 14. Other dimensions of theelectrodes are described hereinbelow, with reference to FIGS. 2-3.

FIG. 1 shows a schematic illustration of electrode 64, in accordancewith some applications of the present invention. As shown, the insulatedportion 68 of electrode 64 includes an elliptical proximal base portion66 and an elongated body portion 65 extending between the base portionand the exposed tip 70. Tip 70 typically comprises distal tip 72 and tipbase 74. Base portion 66 typically has a major axis W1 of between 25 umand 200 um, e.g., 100 um, and a minor axis W2 that is typically 10-100um, e.g., 50 um. Base portion 66 typically has a larger average diameterthan body portion 65, contributing to the structural strength ofelectrode 64. Body portion 65 is typically generally elliptical, and hasa major axis W3 of between 15 um and 60 um, e.g., 30 um, and a minoraxis W4 between 5 um and 20 um, e.g., 10 um. Typically, electrodes 64have a cross-section of 50-200 um2, 20 um from distal tip 72. For someapplications electrodes 64 have a cross-section of at least 200 um2, 20um from distal tip 72.

For some applications, each electrode 64 is typically 25-100 um inlength e.g., 50 um, in order to penetrate the nerve fiber layer (NFL)and reach the layer of ganglion cells 12 (GCL). Contacting the ganglioncells by electrodes 64 typically enables the use of a reduced amount ofpower in order to stimulate the ganglion cells. Close proximity toganglion cells 12 generally results in more focused stimulation thatenables higher pixel density for a given amount of electrical charge.

Reference is made to FIG. 2A, which is a schematic illustration of anarray 90 of electrode 64, in accordance with some applications of thepresent invention. Tip portions 70 of electrodes 64 are typically shapedto define a plurality of perforations passing therethrough. In someapplications, tips 70 are generally pointed, to facilitate tissuepenetration. The perforated configuration of the tip allows for neuronalprocesses to intertwine with the electrode tips when electrodes 64 aredisposed in retinal tissue of a subject. Increased and direct contactbetween the electrodes and the neuronal processes, improves theinteraction between the neurons, e.g., bipolar cells, and theelectrodes. Improved neuron/electrode interaction and coupling enhancesstimulation of the neurons by the electrodes. Each tip 70 is typicallyshaped to define between 1 and 50 perforations (e.g., 1-10) passingtherethrough. For some applications, the perforations of each electrodeare located 5-20 um (e.g., 10 um) from distal tip 72 and 10-30 um fromtip-base 74.

Typically, a spatial density of the perforations of each pointed tip is0.001-0.02 perforations/um2, or 0.02 to 0.5 perforations/um2, e.g., 0.1perforations/um2. For some applications, each perforation has a diameterof 1-10 um. The diameter of the perforations in electrode 64 allowsaxons of bipolar cells, which typically have an average diameter of 1um, to penetrate and grow through the perforations.

As mentioned hereinabove, for some applications electrodes 64 aredisposed in the layer of ganglion cells 12. In such applications, theaxons of the ganglion cells grow through the perforations in electrodetips 70, increasing coupling between the neuronal processes andelectrodes 64, and improving stimulation of the ganglion cell layer.

The average diameter of the perforations is typically smaller than theaverage diameter of a retinal glial cell, which is typically larger than10 um, preventing glial cells from passing through the perforations inthe electrode. Preventing glial cells from passing through theperforations reduces glial encapsulation of the electrodes, and prolongselectrode function.

The perforations are typically created by use of chemical treatmentse.g., etching and/or a laser beam. For some applications, the sametreatment is used to create the perforations and to increase surfaceroughness. For some applications, a surface of tip 70 of electrode 64 iscoated with carbon nanotubes, attracting neuronal processes to theperforations in tip 70 and increasing adhesion of the neuronal processesto the perforations. Typically, the carbon nanotube coating within theperforation can withstand penetration of neuronal processes into theperforations.

Reference is made to FIG. 2B, which is a schematic illustration of anend view of array 90 of electrodes 64, in accordance with someapplications of the present invention. Device 60 typically comprisesarray 90 of electrodes 64 comprising at least 40 electrodes per mm2,e.g., between 100 and 400 electrodes per mm2. FIG. 2B shows array 90divided into nine units by way of illustration and not limitation. Forsome applications, each unit is 100 um×100 um in size. Each unittypically comprises a pair of bipolar electrodes. For some applications,both bipolar electrodes (+ and −) in each unit protrude from array 90and are configured to penetrate tissue of retina 6. One of theseelectrodes may be stimulating, and the other a return electrode, or elseboth may be stimulating. For some applications, the stimulatingelectrode is longer than the return electrode in each pair, and reachesthe layer of bipolar cells, while the shorter return electrode onlyreaches the NFL layer. For other applications, one electrode (eitherthe + or the −) protrudes from array 90 and is configured to penetratetissue of retina 6, and the other electrode, of opposite polarity, is asurface electrode that is not configured to penetrate tissue of retina6, but rather functions as a return electrode. The distance D1 betweenthe pair of bipolar electrodes 64 in each unit is typically between 5and 50 um, e.g., 10 um. The distance D2 between electrodes of adjacentunits is typically between 25-100 um, e.g., 50 um. Generally, thedistance D1 between a pair of electrodes in each unit is smaller than(e.g., less than half of) the distance D2 between electrodes of adjacentunits.

Reference is made to FIGS. 1 and 2A-B. As shown in FIG. 2B, which is a Zview from the distal tip 72 of electrodes 64, the major axis W1 of baseportion 66 of insulated portion 68 is typically 1.5-2.5 (e.g., 2) timeslarger than the minor axis W2 of body portion 65. Typically, major axisW1 is 25-200 um, e.g., 50-150 um (e.g., 100 um), and minor axis W2 is10-100 um, e.g., 20-80 um (e.g., 50 um)

Reference is again made to FIGS. 1 and 2A-B. As mentioned hereinabove,for some applications, electrodes 64 comprise bipolar electrodes thatare configured to penetrate retinal tissue of a subject. Penetratingbipolar electrodes, which are typically implanted such that both thestimulating and return electrodes are in close proximity to a neuronalretinal cell, require a smaller potential between the electrodes andenable reaching a higher potential drop across a given cell, resultingin enhanced stimulation of the cell. This is in contrast to manyepi-retinal implants known in the art in which neuronal cells of theretina are stimulated by a surface electrode on the ILM layer.

For some applications, an array 90 of electrodes 64 is divided intosubsets of electrodes. For such applications, a subset of three or more,e.g., 3-6, stimulating electrodes, by way of illustration and notlimitation, surround and share a common return electrode 8. Eachelectrode in the subset receives a signal, through driving circuitry,from a discrete, respective, photosensor in support substrate 62, and inresponse, stimulates the retina of the subject. In such applications,the return electrode typically has a sufficiently large surface area inorder to accommodate the electric charge returning from the subset ofstimulating electrodes. Generally, such an arrangement of array ofelectrodes 64 enables the use of a reduced number of electrodes, sinceseveral stimulating electrodes share a common return electrode. For someapplications, the stimulating electrodes are configured to driveelectrical charges into the cells of retina non-simultaneously. Suchstaggering of the driving of each electrode in the subset reduces theamount of return electrical charge that is driven through the returnelectrode at a given time. For some applications, array 90 comprises atleast 10 subsets of electrodes, e.g., 100-500 subsets. For someapplications, array 90 comprises 500-1500 subsets of electrodes.

Reference is again made to FIGS. 2A-B. Electrodes 64 are typicallyfabricated by conventional fabrication processes known in the art. Forsome applications, following fabrication, electrodes 64 are assembled onarray 90 by methods such as “pick and place.” For other applications,other methods are used to fabricate array 90 of electrodes 64, e.g.,three dimensional etching and/or MEMS Palladium etching technique. Forsome applications, techniques described in one or more of the followingpatents are practiced in combination with techniques and apparatusdescribed herein: U.S. Pat. No. 7,096,568, U.S. Pat. No. 6,678,458, U.S.Pat. No. 6,923,669, U.S. Pat. No. 6,473,365, U.S. Pat. No. 6,762,116U.S. Pat. No. 7,025,619, U.S. Pat. No. 7,081,630 and U.S. Pat. No.6,677,225 which are incorporated herein by reference.

Reference is now made to FIG. 3, which is a schematic cross-sectionalillustration of a tip portion 70, in accordance with some applicationsof the present invention. Intraocular device 60 comprises electrodeswhich, for some applications, are shaped to define respective pointedtips configured for penetrating tissue of the subject. Each tip 70 istypically an electrically exposed tip, configured to directly driveelectrical charge into the retinal tissue, e.g., bipolar cells, causingstimulation of the tissue and resulting in enhanced vision. Exposed tip70 of the electrode typically has a length L2 of between 25 um and 100um, e.g., 50 um. Typically, although each tip 70 is pointed when viewedfrom a distance, and thus functions as a pointed tip for purposes suchas penetrating tissue, a close examination of the tip 70 reveals that itis shaped to have a radius of curvature R of 0.5-10 um, e.g., 2 um.

Tip 70 may be shaped to define a tip having an angle alpha of 30-60degrees. As shown in FIG. 3, tip 70 comprises a tip-base portion 74 anda distal tip 72. Base portion 74 of tip 70, which is at a distal end ofthe electrode body portion, has a width W5 of between 15 um and 60 um,e.g., 30 um. Tip 70 typically decreases monotonically in width along itslongitudinal axis from tip-base portion 74 to distal tip 72, until itreaches a width W6 of between 1 um and 20 um, e.g., 10 um, 4 um proximalfrom distal tip-end 72. For some applications, tip 70 is reduced in sizeafter electrode shaping by techniques such as laser ablation.

As shown in FIG. 3, tip 70 typically decreases monotonically inthickness along its longitudinal axis from base portion 74 to distal tip72. Base portion 74 of tip 70 has a thickness T1 of between 5 um and 20um, e.g., 10 um. Distal tip 72 of tip 70 has a thickness T2 of between0.5 um and 5 um, e.g., 2 um. The shape of the distal tip of tip 70, anda radius of curvature R of tip 70, typically reduces the extent to whichtip 70 penetrates and/or ruptures cells with which it comes in contact.Typically, retinal neuronal cells range between 5 and 10 um. Radius ofcurvature R is typically 0.5 um-10 um, e.g., 2 um, roughly in the samemagnitude as the cells. Generally, all edges of electrode tip 70 andelectrode 64 have a radius of curvature that is greater than 0.1 um,e.g., greater than 0.5 um. Rounding of the edges is typically done toreduce concentration of charge at sharp edges. Surface treatments toincrease roughness of a surface of tip 70, as described hereinbelow, arealso used to smoothen and round edges of tip 70 and electrode 64.

Typically, tip 70 of electrode 64 is treated to increase surfaceroughness of tip 70. For some applications, an area 73 of tip 70 istreated to increase roughness, whereas another area 75 of tip 70 remainsuntreated in order to maintain structural strength of the tip.

Reference is made to FIGS. 2A-B and 3. As shown in FIG. 3, untreatedareas 75 are maintained in order to strengthen tip 70 for withstandingcompression forces applied during penetration of tip 70 into retinaltissue. Surface treatment of the tip in areas 73 typically affects anarea of the tip that is as deep as 2 um from the surface. Increasedsurface roughness causes an increased surface area of the tip. The tipis treated to increase roughness such that 1 mm2 area has an equivalentsurface area of between 10 mm2 and 1000 mm2, e.g., 100 mm2. Increasedsurface area generally reduces electrode impendence, thereby enhancingstimulation of retinal tissue by electrodes 64. Additionally, increasedroughness generally reduces surface charge density and improveselectrode capacitance, enabling an increase in the charge injectionlimit. Increased surface roughness to reduce charge density is typicallyachieved by techniques of nanofabrication and/or metal etching, asdescribed in Liang et al., in an article entitled “Surface modificationof cp-Ti using femtosecond laser micromachining and the deposition ofCa/P layer” Materials Letters Volume 62, Issue 23, 31 Aug. 2008, Pages3783-3786, which is incorporated herein by reference.

For some applications, electrodes 64 are coated with carbon nanotubes.Typically, carbon nanotubes create a rough surface in electrode 64,including tip portion 70. Rough surfaces in general and carbon nanotubesurfaces in particular have been shown to attract neurons and promoteneuronal growth. As described in an article by Sorkin et al., entitled“Process entanglement as a neuronal anchorage mechanism to roughsurfaces,” Nanotechnology 20 (2009) 015101 (8 pp), which is incorporatedherein by reference, neurons were found to bind and preferentiallyanchor to carbon nanotube rough surfaces. Thus, adhesion of retinalneurons, e.g., bipolar cells, to carbon nanotube electrodes provided bythese applications of the present invention, promotes cell-electrodecoupling and/or axon regeneration, leading to improved stimulation ofthe retina. For some applications, the carbon nanotube coating ofelectrode 64 is glued to the electrode surface and/or grown on aselected surface of the electrode by using doping techniques known inthe art.

For some applications, a femtosecond laser is used to increase surfaceroughness of electrodes 64. Femtosecond laser treatment produces roughsurface structures on titanium possibly for the use of implants andother biomedical applications treatments (Vorobyev et al., 2007referenced above). As described in an article by Vorobyev et al.,entitled “Femtosecond laser structuring of titanium implants,” AppliedSurface Science, Volume 253, Issue 17, 30 Jun. 2007, Pages 7272-7280,which is incorporated herein by reference, femtosecond laser treatmentincreases the roughness of a titanium substrate in the range of 1-15 um.Additionally, femtosecond laser treatment was shown to produce a varietyof surface nanostructures, such as nanoprotrusions and nanopores on thetitanium substrate. Liang et al., 2007, cited above, report goodbioactivity of a pure titanium substrate that was treated with afemtosecond laser to increase roughness of its surface.

For some application, a blanket etch MEMS procedure is used to increasesurface roughness of electrodes 64. For such applications, the entireelectrode 64 is blanketed and tip 70 is etched to increase surfaceroughness and achieve a desired aspect ratio in a similar procedure tothat described in U.S. Pat. No. 6,770,521 to Visokay.

Reference is made to FIGS. 4A-B, which are schematic illustration ofintraocular device 60, in accordance with some applications of thepresent invention. Device 60 typically comprises an array 1090 ofprotruding electrodes 1064 configured to penetrate the retina of asubject. It is to be noted that techniques and apparatus describedherein with reference to electrodes 64 and array 90 apply to electrodes1064 and array 1090, and vice versa, except where otherwise indicated.For some applications, electrodes 1064 vary in length. Electrodes 61 aregenerally longer than electrodes 62, thereby facilitating directstimulation of distinct areas of the retina, e.g., layer of the bipolarcells and/or the layer of ganglion cells. Other dimensions of theelectrodes are described hereinbelow, with reference to FIG. 6.

Electrodes 1064 comprise any suitable material e.g., palladium and/ortitanium, and/or silicon electrodes. For some applications, electrodes1064 comprise a metal alloy and/or doped electrodes. Typically, asilicon wafer 1030 forms the base of array 1090 from which electrodes1064 protrude. For some applications, wafer 1030 is selectively etchedto a desired depth by using any suitable technique known in the art,e.g., techniques of Deep Reactive Ion Etching (DRIE). For someapplications, following bonding of the silicon wafer, electrodes 1064are etched by using any suitable technique known in the art, e.g.,techniques of Deep Reactive Ion Etching (DRIE), to have desireddimensions and aspect ratios. For some applications, additional metalssuch as platinum, and/or palladium, are deposited on electrodes 1064 byusing, for example, a shadow mask technique. An attaching titanium ringframe 1020 is typically electroplated with electrodes 1064 to formstructure that can subsequently be welded to the metal ring case 2020(shown in FIG. 5). The silicon wafer 1030 is typically biocompatible.Ring frame 1020 is typically bonded to silicon wafer 1030, by using,e.g., fusion bonding. Suitable fusion bonding techniques are describedin an article by Jourdain et al., entitled, “Fabrication ofpiezoelectric thick-film bimorph micro-actuators from bulk ceramicsusing batch-scale methods,” which is incorporated herein by reference.Wafer 1030 typically comprises through-wafer vias.

Typically, device 60 additionally comprises a CMOS chip 1040 includingthrough-silicon vias. For some applications, solder bumps 1050 aredeposited on an upper side of CMOS chip 1040, electrically connectingchip 1040 to silicon wafer 1030. Additionally, for some applications,device 60 comprises a layer 1060. Layer 1060 typically comprisesadditional elements of an intraocular retinal prosthesis, e.g., anenergy receiving layer, a photosensor layer and driving circuitry thatis powered by the energy receiving layer. The driving circuitrytypically drives electrical charge into the retinal tissue from therough tips 1070 of electrodes 1064, in response to sensing by thephotosensor layer, in order to stimulate the retinal tissue. Theelectrical signal generated by layer 1060 is typically routed throughsilicon wafer 1030 to electrodes 1064, providing sealing on one side andelectrical contact on the other.

For some applications, a back side of the titanium wafer is bound to aglass cap 80 which, as shown in FIG. 4B, encapsulates the entirety ofintraocular device 60, excluding array 1090 of protruding electrodes1064. For some applications, glass cap 80 comprises two distinct glasspieces, one of which is shaped to define a hole. The glass pieces aretypically bonded to each other by anodic bonding, forming a single glasscap 80. Bonding of titanium frame 1020 to glass cap 80 is optionallydone using thermal compression bonding. This low temperature bondingstep generally does not affect circuitry of intraocular device 60. Glasscap 80 generally reduces exposure of human tissue to any toxicmaterials, e.g., contaminated silicon, which may exist in intraoculardevice 60. Typically, laser welding is used to close the glassencapsulation.

Reference is made to FIG. 5, which is a schematic illustration ofintraocular device 60, in accordance with some applications of thepresent invention. As described hereinabove, intraocular device 60typically comprises array 1090 of electrodes 1064, which are configuredto penetrate retinal tissue of a subject. For some applications,electrodes 1064 comprise long electrodes 61 and short electrodes 62.Array 1090 is typically bonded to silicon wafer 1030 which is coupled toCMOS chip 1040 via solder bumps 1050. As shown in FIG. 5, for someapplications, intraocular device 60 comprises a metal ring 2020 whichencapsulates the entirety of intraocular device 60, excluding array 1090of protruding electrodes 1064. For some applications, metal ring 2020functions as DC grounding for electrodes 1064. Additionally, in a casein which an electrode is not active, it may be held to ground byactivating a switch that locks the electrode to metal ring 2020, suchthat the electrode stays at ground.

Reference is now made to FIGS. 1 and 5. As described hereinabove withreference to FIG. 1, each electrode in intraocular device 60 comprisesan electrically-insulated body portion coupled to an electricallyexposed distal tip. FIG. 5 shows an exploded view of electrodes 1064showing body portion 1068 of electrodes 1064 coated with a polyimideinsulating coating 82. Tip 1070 of electrode 1064 remains electricallyexposed, i.e., not coated with a polyimide coating, to enable anelectrical connection between the tip and the bipolar layer (or otherportions of the retina). As described hereinabove, in some applications,tip 1070 physically contacts the layer of bipolar cells 14 whenintraocular device 60 is implanted in the eye of a subject. For someapplications, the entire electrode is fabricated to include a polyimidecoating, followed by for example, an etching process to selectivelyremove the polyimide coating from electrode tip 1070. Alternatively, thepolyimide coating is removed from the tip 70 by laser ablation. Seo etal., in an article entitled “Biocompatibility of polyimidemicroelectrode array for retinal stimulation,” Materials Science andEngineering: C, Volume 24, Number 1, 5 Jan. 2004, pp. 185-189(5), whichis incorporated herein by reference, report that polyimide is a suitablematerial for a retinal prosthesis.

As described hereinabove with reference to FIG. 3, the electricallyexposed tips of the electrodes are treated to increase surfaceroughness. Accordingly, FIG. 5 shows tip 1070 having a rough surface toincrease neuronal cell adhesion to tip 1070, thus increasing tissuestimulation by electrodes 1064. Typically, tip 1070 is configured topenetrate retinal tissue of a subject.

Typically, intraocular device 60 is configured to match the naturalcurvature of the retina to facilitate implantation and anchoring ofintraocular device 60 to the retina. Accordingly, electrodes 1064typically vary in length, and as indicated by FIGS. 4A-B and 5, for someapplications, tips 1070 of electrodes 1064 together define a convexcurved surface having a radius of curvature that is 6-15 mm.

Reference is made to FIG. 6 which is a schematic illustration of asection of array 1090 of electrodes 1064, in accordance with someapplications of the present invention. As shown, array 1090 typicallycomprises electrodes 1064 of varying heights. For some applications,electrodes 1064 are arranged in concentric circles on wafer 1030. Thecircles of electrodes 1064 typically alternate between long electrodes61 and short electrodes 62, such that electrodes 1064 are typicallyarranged in pairs of bipolar electrodes. Each pair of electrodestypically comprises a single long electrode 61 and a single shortelectrode 62.

Intraocular device 60 and electrodes 1064 are typically configured tomatch the natural curvature of a human organ and/or tissue in which itis implanted, e.g., the retina. As shown in FIG. 6, for someapplications, electrodes 1064 vary in length. Electrodes 61 aregenerally longer than the electrodes 62, thereby facilitating directstimulation of distinct areas of the retina, e.g., layer of bipolarcells and/or the layer of ganglion cells. For some applications, longelectrodes 61 have a length L3 of 200-800 um, e.g., 300-500. Shortelectrodes 62 typically have a length L4 of 100-550 um, e.g., 150-350.Typically long electrodes 61 are 50-150 um longer than the adjacentshort electrodes 62. For some applications, both long electrodes 61 andshort electrodes 62 function as stimulating electrodes. For otherapplications, long electrodes 61 function as stimulating electrodes andshort electrodes 62 function as return electrodes. For someapplications, return electrodes 62 are less than 10 um in length, andmay even comprise surface electrodes. In this case, L4 is less than 5 umin length.

Reference is made to FIG. 7, which is a schematic illustration of device60 disposed in retina 6, in accordance with some applications of thepresent invention. FIG. 7 shows components of device 60 (silicon wafer1030, attaching ring frame 1020, CMOS chip 1040, solder bumps 1050 andlayer 1060) in glass encapsulation 80. Electrodes 1064 are shownpenetrating retina 6. For some applications, and as describedhereinabove with reference to FIG. 6, electrodes 1064 of intraoculardevice 60 are arranged in pairs of bipolar electrodes. For someapplications, both bipolar electrodes (+ and −) of each pair protrudefrom intraocular device 60, and are configured to penetrate tissue ofretina 6. For some applications, the electrodes in each pair are ofvarying lengths, such that one electrode (either the + or the −) islonger than the second electrode. Typically, the longer electrode 61(e.g., 200-800 um in length) is configured to protrude from intraoculardevice 60 and penetrate retinal tissue in order to contact and stimulatethe bipolar cell layer. The shorter electrode 62 (e.g., 100-550 um inlength) is typically configured to protrude from intraocular device 60in order to contact and stimulate epi-retinal tissue, e.g., the NFLlayer. Additionally or alternatively, short electrode 62 is configuredto penetrate and stimulate retinal ganglion cells. For someapplications, long electrodes 61 function as stimulating electrodes,e.g., to stimulate the bipolar cells and short electrodes 62 function asreturn electrodes.

For other applications, one electrode (either the + or the −) protrudesfrom intraocular device 60 and is configured to penetrate tissue ofretina 6, and the other electrode, of opposite polarity, is a surfaceelectrode that is not configured to penetrate tissue of retina 6, butrather functions as a return electrode (application not shown).Typically, intraocular device 60 comprises at least 100 short or surfaceelectrodes, and at least 400 long electrodes.

For some applications, electrodes 1064 comprise hook electrodesconfigured to anchor to retinal tissue of a subject, increasing couplingbetween the target cells and the electrode.

Reference is made to FIGS. 1-7. For some applications, intraoculardevice 60, including substrate 62, is flexible and can be adjusted tomatch the natural curvature of the retina during implantation.Intraocular device 60 may be adjusted to match the retina of a subjectby standard fitting and/or can be tailor made according to OCT imagingof the retina. Once adjusted to match the natural curvature of theretina, intraocular device 60 is typically glued and/or stitched inplace. For other applications, intraocular device 60 is generally rigid,and electrodes of varying heights and, optionally, shapes enable properattachment of the intraocular device to the curved structure of theretina.

Reference is again made to FIGS. 1-7. It is to be noted that a pluralityof implantable devices 60 may be implanted in discrete locations intissue of retina 6, either arranged in an array, or, for example,pseudo-randomly. Typically, intraocular device 60 is wireless and doesnot comprise bulky components, facilitating implantation of severalimplants 60 in retina 6 of the subject.

It is to be noted that a system comprising penetrating electrodes withrough and/or perforated tips as described hereinabove with reference toFIGS. 1-7, may be implanted in any other organ (e.g., brain, nose, earsand/or tongue), and used in any other neurological application (e.g.,cortex stimulation). Implantation of penetrating electrodes as describedhereinabove in, for example, brain tissue of a subject typically reducesthe amount of power required to stimulate the tissue. Additionally oralternatively, implantation of such electrodes facilitates specificsensing and enhances specific stimulation of a target neuron in thetissue by directly contacting selective areas with the electrodes.

For some applications, a system comprising penetrating electrodes asdescribed hereinabove may be used to stimulate organs such as the liveror the pancreas. Implanting an array of such electrodes in, for example,selected areas of pancreatic tissue (e.g., insulin-secreting areas)enables specific and more effective stimulation of these areas.

Reference is again made to FIG. 4. For some applications, layer 1060 isa multilayer array comprising an energy receiving layer, a photosensorslayer and driving circuitry that is powered by the energy receivinglayer. The driving circuitry typically drives current into thestimulating electrodes 1064, in response to sensing of ambient light bythe photosensor layer, in order to stimulate the retinal tissue.Alternatively, layer 1060 comprises a single layer array configured bothfor energy receiving and photosensing. For some applications a portionof the single array is configured for energy reception and a separateportion of the array is configured for photosensing. Alternatively, forapplications in which a single layer is configured both for energyreceiving and photosensing, the entire layer is configured, duringalternating time periods, to (a) receive energy from power source 24(shown in FIG. 1) to power the driving circuitry, and (b) sense ambientlight and responsively transmit a signal to the driving circuitry.

Reference is made to FIG. 8, which is a block diagram of thetransmission of energy, information, and instructions, in system 20, inaccordance with some applications of the invention. External device 600is located outside of a body of a subject and comprises power source 24,which emits energy to power components of intraocular device 60. Theenergy which is transmitted to device 60 is received by energy receiver32. Energy receiver 32 typically comprises a voltage regulator 29configured to maintain a constant voltage level to power the componentsof device 60. Intraocular device 60 further comprises photosensors 34configured to detect photons 33 and generate a photosensor signalresponsively to the photons. It is noted that although photosensors 34are generally shown and described herein as being positioned inintraocular device 60, the scope of the present invention includescoupling photosensors 34 to external device 600 (application not shown).For some applications, a single light receiving element indicated by box210 functions, during alternating time periods, as an energy receiver 32and photosensors 34. The photosensor signal is transmitted to drivingcircuitry 36, which drives the electrodes 1064 to apply electricalcharges to cells of retina 6. As shown, system 20 typically comprises acontrol unit 200 configured to regulate operating parameters ofintraocular device 60. For example, the control unit may regulateoperation of photosensors 34.

Typically, photosensors 34 are arranged as an array of photosensors 34.In some configurations of device 60, each photosensor in the array ofphotosensors corresponds to a stimulating electrode in the array ofelectrodes 1064. For some applications, each photosensor functionsindependently, i.e., each photosensor receives photons 33 and inresponse sends signals to driving circuitry 36, whereupon the drivingcircuitry drives the corresponding electrode to apply electrical chargeto the retina 6. Thus, intraocular device 60 comprises an array ofphotosensor units, each photosensor unit comprising a photosensor and acorresponding electrode. Accordingly, the degree of retinal stimulationapplied by each photosensor unit in the intraocular device is dictatedby the light received by that unit. For some applications, eachphotosensor unit translates the level of light received by that unitinto a train of stimulation pulses that is applied to the retina by theelectrode. Additionally, such conversion of intensity of received lightto frequency of stimulation can include a log transformation, such thatfor example: x photons received by the photosensor unit translate intoone stimulation pulse applied by the electrode, while 10x photonscorrespond to only 2 stimulation pulses applied by the electrode.

Although functioning independently from one another, for someapplications, a central control unit 200 regulates the function of eachphotosensor and corresponding electrode unit. Additionally oralternatively, each photosensor unit is configured to communicate withother units located in close proximity, and to modulate the electricalcharge it drives into the retina in response to the functioning ofneighboring units. Regulation of the electrical charge applied by eachunit in the array of photosensors 34 with respect to other units in thearray facilitates regulation of diverse features of visual perception.Varying the electrical charges applied to retinal neurons allowsimproved processing of the electrical charge by the retinal neuronse.g., bipolar cells.

For some applications, processing is performed by control unit 200. Insome configurations of intraocular device 60, there is a larger numberof photosensors than stimulating electrodes. For example, processing bycontrol unit 200 can include disabling a bad pixel, improving focus ofan image, sharpening, level adjustment, edge enhancement, and motiondetection. Typically, this is performed using the data provided by thesignificantly larger number of photosensors than stimulating electrodes.Thus, edge detection and enhancement (or other image processingtechniques) are performed using the hundreds of data points (or more),which are available to the control unit after having been sampled by theindividual photosensors. This processing is used to allow the smallernumber of stimulating electrodes to apply a more meaningful form ofretinal stimulation, which reflects the output of the image processing(e.g., by showing an enhanced edge, emphasizing motion, or sharpeningindividual elements of an image). The scope of the present inventionincludes performing any of the image processing techniques describedherein, even if the number of photosensors is not smaller than thenumber of stimulating electrodes. For some applications, a standardprocess is utilized in order to, e.g., enhance sensitivity by summation,edge detection for a clearer image, noise reduction in time and space,and/or adaptive dynamic range. Alternatively, the control unitfacilitates processing, such as edge enhancement, by horizontal and/oramacrine cells of the retina, by providing a simpler image than thatimaged by the photosensors. This simpler image is more easily processedby the retina neuron network.

For some applications, intraocular device 60 comprises protrudingelectrodes which are sufficient in length to contact bipolar cells 14(shown in FIG. 1), thereby directly driving electrical charges into thebipolar cells. Thus, the electrical charge from the electrodes isdirectly driven into the bipolar cells, which transmit the viewed imagevia the ganglion cells and the optic nerve to the brain. Additionally,other retinal neurons, e.g., horizontal cells and/or amacrine cells,perform image processing to enhance and improve the received image.Examples of such processing include: focusing, edge detection, lightadjustment, averaging, and motion detection. By directly contacting thelayer of bipolar cells, device 60 mimics the natural transferring of asignal from native photoreceptor cells directly to the bipolar cells,for processing by the bipolar cells. The photoreceptor nerve cells aretypically connected by synapses to bipolar nerve cells, which are thenconnected to ganglion nerve cells 12. The ganglion nerve cells connectto the optic nerve fibers, which carry the information generated in theretina to the brain.

For some applications, device 60 may comprise protruding electrodes thatare shorter in length (e.g., 50-200 um, e.g., 100-150 um) and configuredto directly contact the layer of ganglion cells 12 (shown in FIG. 7).For some applications, control unit 200 is configured to performprocessing of the signals from the photosensors, and directly apply thepre-processed electrical charges via the electrodes to the ganglioncells, e.g., as described hereinabove with respect to improving edgedetection or other image processing techniques.

Reference is again made to FIG. 8. For some applications, centralcontrol unit 200 regulates the function of some or all photosensors 34and their corresponding electrode(s) 1064, e.g., by controlling theduration of a sensing period of each photosensor. Typically, the amountof ambient light that lands on the array of photosensors is used by thecentral control unit to determine the duration of a sensing period ofeach photosensor, i.e., the amount of time in which the photosensorreceives photons before the driving circuitry drives the correspondingelectrode to drive electrical charge into retinal tissue (e.g., 0.1ms-30 ms). Thus, for example, the sensitivity of each photosensor may beincreased over the course of several seconds, if the subject enters adark room.

Additionally or alternatively, central control unit 200 sets theduration of an energy receiving period, i.e., the amount of time inwhich energy receiver 32 receives energy from external power source 24before that energy is passed to driving circuitry 36 to drive theelectrodes to drive electrical charges into retinal tissue (e.g., 1-10ms, or 10-100 ms). For example, control unit 200 may increase theduration of an energy receiving period to supply device 60 with asufficient amount of energy, e.g., if the subject increases theintensity such that a larger amount of electrical charge is appliedthrough the electrodes, resulting in device 60 requiring an increasedamount of energy. Further additionally or alternatively, central controlunit 200 regulates the stimulation timing.

Reference is still made to FIG. 8. For some applications, in addition tosupplying power to device 60, the energy emitted by power source 24 isused to regulate operation of intraocular device 60. This regulation maybe in real-time, e.g., where the duration of each laser pulsecorresponds to the duration of stimulation applied by an electrode tothe retina. Alternatively, this regulation is not in real-time, e.g.,conveying a digital message to the controller, which, in turn, modulatesthe stimulation signal (for example to increase exposure time). In someapplications, external device 600 comprises a control element 27 (e.g.,a dial, switch, or button) coupled to eyeglasses 25 (shown in FIG. 1),allowing the subject to interactively control the intensity of theelectrical charge applied to retina 6 and/or the sensitivity ofphotosensors 34 to received light, and/or another system parameter.Typically, the intensity of the electrical charge applied to the retinaby the electrodes is determined by driving circuitry 36, which driveselectrodes 1064 to apply the electrical charge in pulses of electricalcharge. The driving circuitry is configured to alter the intensity ofelectrical charge applied to the retina by regulating a stimulationparameter such as a number of the pulses, a frequency of the pulses,duration of each pulse, or a pulse repetition interval of the pulses.Additionally or alternatively, the driving circuitry is configured tocontrol amplitude of the electrical charges applied by the electrodes.Control unit 200 is configured to regulate the function of the drivingcircuitry to adjust the intensity of the electrical charge based on thesubject's input. Additionally, for some applications, the sensitivity ofphotosensors 34 to received light is determined by the duration of asensing period of photosensors 34. Control unit 200 is configured toincrease or decrease sensitivity of device 60 in response to thesubject's input, e.g., by regulating the duration of a sensing period.

For example, if the subject determines that the overall stimulationbeing applied by device 60 to the retina is too strong, then he canadjust a setting on the control element to reduce the stimulationstrength. Similarly, if he senses that his entire visual field isover-stimulated, indicating that the sensitivity of photosensors 34 istoo high (e.g., resulting in the entire array of electrodes activatingthe retina at high intensity), then he can adjust another setting on thecontrol element to reduce the sensitivity. In response to the subject'sinput, the energy emitted by the power source is modulated to regulateoperating parameters of device 60, e.g., to increase or decreaseintensity and/or sensitivity. An example of a suitable modulationprotocol includes a first train of six short pulses from power source24, indicating that stimulation intensity is going to be changed,followed by a train of between one and ten longer pulses indicating asubject-selected desired level of stimulation intensity. To changesensitivity, a first train of six long pulses is emitted from powersource 24, followed by a train of between one and ten longer pulsesindicating a subject-selected desired level of sensitivity. A person ofordinary skill in the art will appreciate that other encoding protocolsmay be used, as well.

For some applications, intraocular device 60 (e.g., the control unit ofdevice 60) is configured to regulate the operation parameter of device60 based on amplitude modulation of the light emitted by the powersource 24 and received by energy receiver 32. Typically, the amplitudemodulation varies between a minimum signal level and a maximum signallevel. For some applications the minimum signal is at least 20% of themaximum signal (e.g., at least 50% of the maximum level). Typically thelight emitted by power source 24 is modulated such that a carrierfrequency of the modulated light is 10-100 kHz and a pulse width ofpulses of the modulated light is 1-10 usec. For some applications,frequency modulation of the emitted light is used instead of or inaddition to amplitude modulation.

In some applications, the minimum signal level is at least 20% (e.g., atleast 50%) of a summed strength of (a) light received by intraoculardevice 60 from power source 24 and (b) ambient light received by theintraocular device. For some applications, external device 600 comprisesa sensor configured to sense a level of ambient light and change themodulation of the light emitted by the power source 24 accordingly. Forsome applications, control element 27 coupled to eyeglasses 25 (shown inFIG. 1), comprises this sensor, e.g., a photodiode, configured to sensethe level of the ambient light. For some applications, intraoculardevice 60 comprises the sensor that senses the level of ambient light.

Alternatively or additionally, a filter, e.g., a narrow band filter, isassociated with energy receiver 32 and is configured to substantiallyprevent the ambient light from reaching the energy receiver or beingsensed by the receiver.

Typically, central control unit 200 receives modulated energy fromenergy receiver 32, and demodulates the energy to regulate operation ofdevice 60 accordingly. For example, based on the subject's input, theenergy emitted by power source 24 is modulated to signal to device 60 todecrease or increase sensitivity of photosensors 34. (For example, themodulation may include changes in pulse timing of pulses emitted bypower source 24.) Control unit 200 is configured to demodulate theenergy received by energy receiver 32 and, for example, accordinglydetermine the duration of a sensing period of the photosensors, i.e.,the amount of time in which the photosensors receive photons before thedriving circuitry drives the corresponding electrode to drive electricalcharge into retinal tissue (e.g., 0.1 ms-5 ms, or 5 ms-100 ms). Thisthereby increases or decreases the sensitivity of the photosensorsaccording to the subject's input. Additionally or alternatively, controlunit 200 is configured to demodulate the energy received by energyreceiver 32 and accordingly regulate the driving circuitry to alter theintensity of electrical charge applied to the retina by altering astimulation parameter such as a number of the pulses, a frequency of thepulses, duration of each pulse, and a pulse repetition interval of thepulses.

Alternatively, the function of elements and/or arrays and/or sub-arraysof device 60 are controlled by several distributed control units.

For example, for some applications, each photosensor and correspondingelectrode unit is controlled by an individual control unit whichregulates system parameters, such as parameters of the photosensor. Inan application, the sensitivity of the photosensors is regulated, forexample, by setting the duration of a sensing period of each photosensor(i.e., the amount of time in which the photosensor receives photonsbefore the driving circuitry drives the corresponding electrode to driveelectrical charge into retinal tissue). For other applications, separatecontrol units regulate the function of each subset of electrodes andcorresponding photosensors.

Reference is made to FIGS. 1-8. For some applications, device 60 isconfigured to enable night vision (typically in addition to regularvision when there is sufficient light). Typically, photosensors 34 aresensitive to visible light and are configured to receive photons fromambient light and generate a signal in response thereto. For someapplications, and in particular for conditions lacking ambient visiblelight, device 60 additionally comprises uncooled infrared (IR) detectorswhich receive incident IR radiation and produce an output signaldepending on the amount of IR radiation landing on the detector. Theuncooled IR detectors convert the incident IR radiation into anelectrical current in device 60 which is conveyed to the drivingcircuitry, which in turn drives the electrodes to apply electricalcharges to the retina, causing image formation.

Reference is again made to FIGS. 1-8. During implantation, device 60 istypically mechanically attached to the retina of a subject and/or gluedinto place.

Reference is still made to FIGS. 1-8. For some applications, electrodes1064 are arranged in several subsets of electrodes. For someapplications, device 60 comprises 10-2500 subsets, e.g., 100-500 subsetsof electrodes. For some applications, array 1090 comprises 500-1500subsets of electrodes. For some applications, each subset of electrodescomprises three or more electrodes. For some applications, an electrodein at least one of the subsets is within 300 um or 500 um of anotherelectrode in the subset.

Typically each subset of electrodes shares a common power supply, e.g.,a common capacitor, which provides current (typicallynon-simultaneously) to all of the electrodes in a respective subset. Insuch applications, the capacitor in each subset is sufficiently large(e.g., 0.01-0.1 nf, or 0.1 nf-1 nf) to allow charging to less than 50%of full-charge of the capacitor during each charging of the capacitor.Using a large capacitor generally enhances the efficiency of intraoculardevice 60, since it allows for the capacitor to quickly recharge once ithas provided currents to the electrodes. In contrast, using a singlesmall capacitor in order to drive a single electrode typically requiresa longer recharging period and is therefore less efficient. However, itis generally not possible to have one large capacitor per electrode, inan array of 100-1000 electrodes. As provided by some applications of thepresent invention, an array of several subsets of electrodes, in whicheach subset is driven by a respective common large capacitor, allows forthe use of a reduced number of large capacitors, thus allowing the useof a large capacitor to drive a plurality of electrodes and therebyimproving efficiency of the device.

For some applications, electrodes 1064 are arranged in subsets ofstimulating electrodes which surround and share a common returnelectrode (as described hereinabove). At least some of the stimulatingelectrodes 1064 in each subset are configured to drive electricalcharges into the neurons of the retina in non-simultaneous time periods.Consequently, for such applications, the common return electrodereceives electrical charges from at least some of the stimulatingelectrodes in the subset non-simultaneously. Such staggering of thedriving of each electrode and of the returning current generally reducesinterference and neuron load. Such staggering also reduces tissue damageand/or prolongs the lifetime of the return electrode. Additionally, forapplications in which the electrodes are arranged in subsets ofelectrodes, staggering of the driving of each electrode generallyreduces the charge density per subset. Additionally or alternatively,staggering of the driving of each electrode generally reducesinterference between adjacent neuron fibers, typically leading toimproved sensation of vision.

For some applications, no dedicated return electrode is provided, butinstead while one electrode in a subset drives electrical charges intothe retina, some or all of the remaining electrodes in the subset act,collectively, as a return electrode.

Typically, application of electrical charges to the cells may beprogrammed such that generation of sub-harmonics and/or beatfrequencies, and/or artificial frequencies and/or sensations of aflicker are reduced. For example intraocular device 60 may be configuredto apply electrical charge through electrodes 1064 in a subset usingchanging sequences. For example, apparatus 60 may be configured to applyelectrical charge through four electrodes in a subset using the sequence1-2-3-4, followed by applying the electrical charge in a differentsequence (3-1-2-4), by way of illustration and not limitation.Alternatively, the electrical charge is applied using time-basedjittering of at least some of the electrical charge applications, toreduce the generation of sub-harmonics and/or beat frequencies, and/orartificial frequencies and/or sensations of a flicker. For example,instead of applying electrical charge pulses separated by a standardtime gap, the time gap can be “jittered” by introducing a time variationin the frequency of these successive electrical charge pulses.Alternatively or additionally, other signal parameters may be jittered,such as pulse duration and amplitude. For some applications, a fuzzylogic, multi-value, concept is applied. For example, instead of having asingle fixed parameter for power amplitude or jitter, the system has arange of each parameter and it will scan through this range in a regularor pseudorandom procedure. (In biological systems, the exact parameterthat will produce an optimal response at any time is changing, but therange of the parameter is generally known.)

For some applications, system 20 is configured to restore at least somecolor vision in a subject suffering from damaged retinal photoreceptorcells, e.g., cones, by stimulating intact portions of the retina, e.g.,the bipolar cells. Most cones lie in the fovea, which defines the centerof the retina. Humans normally have three types of cones responding todifferent wavelengths. A different signal is applied by the differentcone types, allowing perception of different colors. A typical cone cellforms a synapse with a neuron such as the bipolar cell. Intraoculardevice 60 is configured to drive the electrodes to directly stimulatedifferent bipolar cells resulting in perception of different colors.Additionally or alternatively, the electrical charge driven by theelectrodes into the retina is modulated such that different stimulationpatterns are applied to the retina resulting in the perception of color(e.g., red, green and/or blue). Intraocular device 60 can then becalibrated based on the subject's input as to which stimulation pattern(typically based on varying pulse parameters) creates an optimalperception of color.

Additionally, photosensors 34 are color sensitive and configured todistinguish between certain colors (e.g., red, green and/or blue).Accordingly, electrodes 1064 are typically designated red, green and/orblue (by way of illustration and not limitation), corresponding to thecolors sensed by photosensors 34. According to the sensing of differentcolors, the driving circuitry in intraocular device 60 drives electricalcharges through the corresponding electrodes, resulting in the sensationof different colors (typically after an acclimation and/or trainingperiod).

Reference is still made to FIG. 8. For some applications, energyreceiver 32 and voltage regulator 29 are isolated from photosensors 34,to reduce noise levels in intraocular device 60. Photosensors 34 aretypically highly sensitive to energy levels of less than 1 pW, and areas a result susceptible to noise. Electrical stimulation by contrastcreates relatively high power (0.1-1 uW) electrical signals, for neuronactivation. Accordingly, noise generated by the high power signal istypically filtered from entering into the photosensing circuitry. Suchfiltering is typically implemented in the VLSI electrical design.Additionally, voltage regulator 29 is a main connection between the twocircuits and to reduce noise transfer it is typically divided into twodifferent circuits.

For some applications, power source 24 of the external device comprisesan RF emitting power source. For such applications in which the powersource comprises an RF emitting power source, an intraocular lens (IOL)is implanted in the eye of the subject, replacing the native lens.Typically, an RF receiving coil configured to receive RF energy emittedfrom the power source is incorporated into the IOL (configuration notshown). Incorporation of the RF receiving coil in the IOL, instead ofimplanting such a coil in a small epi-retinal space, generally enablesthe use of a large diameter RF receiving coil (e.g., 8-14 mm indiameter). Additionally, an RF receiving coil which is located in theIOL is in relative close proximity to the RF power source, enabling theuse of a reduced amount of energy. Typically, the macula of the retinais spaced about 4-5 cm from eyeglasses 25 (eyeglasses 25 are shown inFIG. 1), which are coupled to an RF energy source. Thus the IOL with theRF receiving coil is positioned approximately 1.5-2 cm from the RFenergy source. This enables higher RF efficiency than if an RF receivingcoil were implanted in the retina. An intraocular unit comprisingphotosensors, driving circuitry and stimulating electrodes is typicallyimplanted in either an epi-retinal or a sub-retinal location andconfigured to receive the energy from the RF receiving coil. For someapplications, a wire transferring energy from the RF receiving coil tothe intraocular unit extends between the RF receiving coil in the IOLand the intraocular unit.

Reference is made to FIGS. 9A-C, which are schematic illustrations ofsystem 20, in accordance with some applications of the presentinvention.

FIG. 9A is a block diagram of transmission of energy, information, andinstructions, in the system for restoring vision, in accordance withsome applications of the present invention. External device 600 islocated outside of a body of a subject and comprises power source 24,which emits energy to power components of intraocular device 60.Intraocular device 60 is shown in FIG. 9A as comprising at least oneenergy receiving die 32, a CMOS imager die 240 and a custom-made ASICdie 260. The energy which is transmitted to device 60 is received byenergy receiver 32, which typically comprises a plurality of discretephotovoltaic cell dies. Intraocular device 60 further comprises at leastone array of photosensors 34, configured to detect photons 33 emanatingfrom external objects and generate a photosensor signal responsively tothe photons. Typically, the photosensors are incorporated into singleCMOS imager die 240 comprising an imager and an image processor. ThisCMOS imager die may be similar to other low power CMOS imagers known inthe art, and/or may be manufactured by companies such as Micron,OmniVision, ST, Mitsubishi and Kodak. For some applications, imager die240 comprises between 10,000 and 5,000,000 pixels (by way ofillustrations and not limitation). Typically, device 60 comprisesbetween 1000 and 5000 stimulating electrodes.

The photosensor signal is transmitted to driving circuitry 36 whichdrives electrode 1064 to apply electrical charges to cells of theretina. As shown, for some applications, electrodes 1064 are coupled toa custom-made ASIC die 260. Typically, device 60 comprises a custom-madeASIC die 260 which additionally includes a charge pump 280, ademodulator 290, a control unit 2000, and an image processor 310. Energyfrom external power source 24 reaches energy receiver 32 and is passedvia charge pump 280 to power components of intraocular device 60. Thecharge pump generates a higher voltage to be supplied to digitalcomponents of device 60. In addition to supplying power to components ofASIC die 260, charge pump 280 supplies power to imager die 240.Alternatively or additionally, photovoltaic cell dies of energy receiver32 can be cascade wired, and thereby configured to increase voltage andenhance power supply to device 60. Energy from the energy receiver andcharge pump is additionally passed to demodulator 290 and control unit2000 in ASIC die 260. The demodulator typically receives modulatedenergy from energy receiver 32, and demodulates the energy to regulate,together with the control unit, operation of device 60 as describedhereinabove with reference to FIG. 8. For other applications, softwareor hardware in the control unit is configured to demodulate the energyfrom energy receiver 32 to regulate operation of device 60 as describedhereinabove. It is to be noted that techniques and apparatus describedherein with reference to control unit 200 apply to control unit 2000 andvice versa, except where otherwise indicated.

ASIC die 260 further comprises an image processor 310 and is coupled tostimulating electrodes 1064 via driving circuitry 36 (including, forexample, analog amplification functionality). The control unit typicallyregulates processing of the signal generated by photosensors 34 by imageprocessor 310 in accordance with the now demodulated information. Theprocessed photosensor signal is passed to driving circuitry 36, whichdrives stimulating electrodes 1064 to apply electrical charge to theretina of a subject.

For other applications, custom-made ASIC die 260 may, additionally tothe above-mentioned components, also comprise energy receiver 32 and/orphotosensors 34 or any combination thereof.

In an additional configuration, intraocular device 60 comprisescustom-made ASIC die 260 and at least one photovoltaic die whichcomprises energy receiver 32 and photosensors 34.

Typically, ASIC die 260 comprises an integral BIT (built-in test),configured to generate an output when device 60 is implanted in an eyeof a subject and transfer the output either in a wired or wirelessmanner, enabling calibration of device 60 after implantation.Alternatively, the output is used to calibrate device 60 prior toimplantation, e.g., during manufacturing or pre-implantation processing.

Reference is now made to FIGS. 9B-C, which are schematic illustrationsof a particular configuration of the components of device 60, inaccordance with some applications of the present invention. FIGS. 9B-Cshow front and side views, respectively, of device 60 in accordance withsome applications of the present invention. As shown, for someapplications, the photosensors, which are configured to receive visiblelight, are incorporated into a single CMOS imager die. (Applications inwhich a plurality of CMOS imager dies are employed are not shown.) TheCMOS imager die is typically surrounded by a plurality of photovoltaicdies configured to function as energy receivers 32 and receive energyfrom an external power source. Typically operation parameters of eachphotovoltaic die, e.g., the duration of an energy receiving period, isregulated by a discrete control unit coupled to each photovoltaic die.Alternatively, a central control unit regulates operation of thephotovoltaic dies.

CMOS imager die 240 and energy receiving photovoltaic dies 32 aretypically arranged in an array 900, which comprises the front side 910of device 60 (the anterior side, when implanted). Typically, the imagerdie and the photovoltaic dies include a back side thereof, which formsthe active surface 400 of these components. Solder bumps 1050 aredeposited on a back side of array 900, electrically connecting array 900to custom-made ASIC die 260 which typically includes through-siliconvias 1055. Alternatively the dies can be connected with wire bondingtechniques. As shown in FIG. 9C, the ASIC die is coupled to electrodes1064, which form the back side 920 of device 60 (the posterior side,when implanted). Typically device 60 is implanted in an eye of asubject, such that front side 910 of array 900 is facing the pupil,allowing visible light and energy from an external power source tostrike array 900, and electrodes 1064 are positioned in a suitableorientation allowing the electrodes to directly contact and stimulatethe tissue of the retina.

Reference is made to FIG. 10, which is a block diagram of transmissionof energy, information, and instructions, in the system for restoringvision, in accordance with some applications of the present invention.FIG. 10 shows an alternative configuration for intraocular device 60. Insome applications, intraocular device 60 takes on a cellular-basedconfiguration in which it comprises a plurality of cells, i.e., aplurality of the unit labeled 500. For some applications, intraoculardevice 60 comprises 1000-5000 such cells. Typically, each cell comprisesan entire set of components including energy receivers 32, photosensors34, a capacitor 270, a demodulator 290, a control unit 2000, drivingcircuitry 36 and 1-2 electrodes 1064. FIG. 10 shows a plurality ofphotovoltaic units which function as energy receivers 32 and receiveenergy from an external power source, e.g., a laser. For someapplications, several photovoltaic units (shown in FIG. 10 as the threetop photovoltaic units by way of illustration and not limitation)function as energy receivers 32, configured to receive energy from anexternal power source, e.g., a laser, to power the components of eachcell 500. Additionally, for some applications, photosensors 34 (shown inFIG. 10 as the bottom unit by way of illustration and not limitation)are configured to receive photons emanating from an external object.

Reference is made to FIGS. 11A-B, which are block diagrams oftransmission of energy, information, and instructions, in the system forrestoring vision, in accordance with yet another application of thepresent invention. FIGS. 11A-B show external power source 24, whichemits energy to power components of intraocular device 60. For someapplications, a single light receiving element (indicated in FIG. 11A bybox 210) functions, during alternating time periods, as an energyreceiver, configured to receive energy from the external power source,and also as photosensors which are sensitive to visible light. FIG. 11Ashows a central control unit 2000 which functions to regulate theoperation of element 210 and to switch between energy receiving andphotosensing. Central control unit 2000 further regulates the functionof additional components of device 60 as described hereinabove. As shownfor this application, device 60 further comprises a charge pump 280, ademodulator 290, an image processor 310 and stimulating electrodes 1064.

For some applications, intraocular device 60 comprises a plurality offully functional cells 500 as described hereinabove with reference toFIG. 10. FIG. 11B shows a cell generally as described with reference toFIG. 10, with the distinction that each photovoltaic unit functions asboth an energy receiver and a photosensor, during alternating timeperiods. FIG. 11B shows a plurality of light receiving elements 210which function as energy receivers and photosensors, during alternatingtime periods. Typically, while functioning as an energy receiver, eachcomponent 210 receives energy to power device 60 from external powersource 24. While functioning as photosensors, each element 210 istypically sensitive to ambient visible light which strikes components210. As shown, for some applications, each cell 500 is regulated by adiscrete control unit 2000 which is configured to regulate the operationof component 210 as an energy receiver and as a photosensor, duringalternating time periods. Additionally, the control unit is configuredto regulate switching of light receiving element 210 between energyreceiving and photosensing. It is to be noted that for some applicationselement 210 is configured to receive other forms of energy, e.g., RFenergy, to power components of intraocular device 60.

For some applications, the plurality of cells 500 are arranged inclusters of cells. Typically, the receiving of energy from the powersource, and the receiving of visible light from an object, occur in twophases. For example, during a first phase, cells 500 in a clusterreceive visible light and during a second phase receive energy from thepower source, e.g., IR energy. The visible light received during thefirst phase is then used to define tissue stimulation during the secondphase. Typically, the stimulation of each electrode in a given clusteroccurs in sequence, in order to reduce short-term power requirements.Thus, for example, if there are four cells in a cluster, then during thesecond phase, each cell is actuated, in turn, to apply tissuestimulation in accordance with the light sensed by the photosensor ofthat cell.

Reference is made to FIGS. 9-11. Energy receivers 32 and/or photosensors34 may comprise diodes selected from the group consisting of: a silicondiode, an amorphous silicon diode, a CMOS diode, a CMOS imaging 3-diodecell or a CMOS imaging 4-diode cell. Typically, any of these may befabricated as back-illuminated energy receivers or photosensors, whichallow passage of light through the substrate before striking the activesurface. For such applications, fabrication techniques ofback-illuminated sensors, which are described in one or more of thefollowing references, are practiced in combination with techniques anddevice described herein:http://www.sony.net/SonyInfo/News/Press/200806/08-069E/index.html; andSwain P K., et al., in an article entitled “Back-Illuminated ImageSensors Come to the Forefront. Novel materials and fabrication methodsincrease quality and lower cost of sensors for machine vision andindustrial imaging.” Photonics Spectra August 2008.

Reference is made to FIGS. 1-11. For some applications, the electrodesdescribed herein function to achieve biphasic stimulation of the cells.For example, the intraocular device may generate for example threevoltages (e.g., 0 V, 1.5 V, and 3 V). A “ground” electrode is connectedto the intermediate voltage, and a stimulation electrode is switchedrepeatedly between the higher voltage and the lower voltage, in order toproduce biphasic stimulation. For some applications, a single voltagedifference is generated (e.g., such that 0 V and 1.5 V are available)and this voltage difference is repeatedly switched to be in alternatingelectrical contact with two of the electrodes, so as to produce biphasicstimulation.

Reference is made to FIGS. 1-11. For some applications, a total volumeof the intraocular device is less than 0.2 cc.

The scope of the present invention includes embodiments described in thefollowing patent applications, which is incorporated herein byreference. For some applications, techniques and apparatus described inthe following patent application are combined with techniques andapparatus described herein:

-   -   US Patent Application Publication 2010/0204754 to Gross et al.,        entitled, “Retinal Prosthesis,” filed Feb. 9, 2009, now issued        as U.S. Pat. No. 8,150,526 to Gross et al.    -   U.S. patent application Ser. No. 12/687,509 to Gefen et al.,        entitled, “Penetrating Electrodes for Retinal Stimulation,”        filed Jan. 14, 2010, now published as U.S. Patent Pub. No.        2011/0172736 to Gefen et al.    -   PCT Application Publication WO 2010-089739 to Gross et al.        entitled “Retinal Prosthesis,” filed Feb. 3, 2010, now published        as WO/2010/089739 to Gross et al.    -   U.S. patent application Ser. No. 12/852,218 to Gefen et al.,        entitled, “Retinal prosthesis techniques”, filed Aug. 6, 2010,        now published as U.S. Patent Pub. No. 2012/0035725 to Gefen et        al.

For some applications, techniques described herein are practiced incombination with techniques described in one or more of the referencescited in the list above, as well as in the remainder of thespecification, all of which are incorporated herein by reference.

It will be appreciated by persons skilled in the art that the presentinvention is not limited to what has been particularly shown anddescribed hereinabove. Rather, the scope of the present inventionincludes both combinations and subcombinations of the various featuresdescribed hereinabove, as well as variations and modifications thereofthat are not in the prior art, which would occur to persons skilled inthe art upon reading the foregoing description.

The invention claimed is:
 1. Apparatus comprising: a light sourceconfigured to emit non-visible light, and to be disposed external to ahuman eye; an intraocular device, comprising at least one receiverconfigured for implantation in the human eye, the at least one receiverhaving an image reception portion and an energy reception portionconfigured to receive a power signal from a non-visible light beamemitted from the external light source; and at least one control unitconfigured to prevent reception of at least a portion of the powersignal by the image reception portion.
 2. The apparatus according toclaim 1, wherein the control unit is configured for implantation in theeye.
 3. The apparatus according to claim 1, further comprising a filter,wherein the control unit is configured to prevent energy reception bysending a control signal to activate the filter.
 4. The apparatusaccording to claim 1, wherein the control unit is configured to preventenergy reception, by sending a control signal to deactivate the imagereception portion.
 5. The apparatus according to claim 1, wherein theenergy reception portion is additionally configured to receive visiblelight.
 6. An intraocular device configured for epi-retinal implantationin a subject's eye, and configured for use with a plurality ofphotosensors, each photosensor configured to detect ambient photons andto generate a signal in response thereto, the intraocular devicecomprising: a plurality of stimulating electrodes configured topenetrate a retinal layer of the subject's eye; and driving circuitry,coupled to the photosensors, and configured to drive the electrodes toapply electrical pulses to a retina of the eye in response to the signalfrom the photosensors, wherein the driving circuitry is configured tovary a frequency of the pulses based on intensity of the ambient photonsreceived by the photosensors.
 7. The intraocular device according toclaim 6, wherein the intraocular device comprises the plurality ofphotosensors.
 8. The intraocular device according to claim 6, whereinthe driving circuitry is further configured to vary a parameter of theelectrical pulses selected from the group consisting of: a number of thepulses, a duration of each pulse, and a pulse repetition interval of thepulses.
 9. The intraocular device according to claim 6, wherein thedriving circuitry is configured to reduce sub-harmonics by jittering thepulse frequency.